A computer security researcher has released a plugin for Firefox that provides a wealth of data on Web sites that may have been compromised with malicious code.

Number of compromised websites up 225 percent

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A computer security researcher has released a plugin for Firefox that provides a wealth of data on websites that may have been compromised with malicious code.

The plugin, called Fireshark, was released at the Black Hat conference. The free open-source tool is designed to address the shortcomings in other programs used to analyse malicious websites, said Stephan Chenette, a principal security researcher at Websense, which lets Chenette develop Fireshark in the course of his job.

Hackers often target legitimate websites with code that can either infect a machine with malicious software or redirect a user to a bad web page.

Websense specialises in detecting web pages that have been infected, as many site administrators don't know that their sites are harmful to visitors or have difficulty reverse-engineering malicious code. Fireshark will "show you the exact details of a mass compromise", Chenette said.

Over the last 12 months, the number of newly compromised websites has increased about 225 percent, Chenette said. "That means attackers are controlling more content that ever before that is being fed to users."

Fireshark must be run in a virtual machine in order to prevent an infection. Users can input a list of websites for investigation. Fireshark then exposes the websites' code.

That harmful code is often obfuscated, so it is difficult to tell what it actually does, Chenette said. But the obfuscated code has to run in the browser in order to work. Fireshark exposes the code, which normally can't be viewed, when it runs in the browser's memory.

"I became frustrated at the publicly available tools," Chenette said. "I heard the outcry from the community that there are not the correct tools to reverse the obfuscated content."

Once the code has been exposed, it's then possible to do more investigation and see if other websites are affected, Chenette said. Fireshark will show vulnerabilties and exploits on websites.

Many websites will be infected with code that either delivers malware or redirects users to bad websites. The tools also generate maps of those redirections, which can give clues as to who may be behind the attacks.

Fireshark collects the data in a '.yml' file, which is similar to an XML file, Chenette said. The '.yml' file can then be integrated into other security analysis tools, Chenette said. The data that Fireshark collects is all held locally, and none of it is shared with Websense.